1. Field of Invention
The present invention relates to novel color filtering for projection systems. More particularly, the present invention relates to a projection system having variable luminosity, a projection system that filters a light beam from a light source multiple times, and novel color wheel designs. The invention is related to U.S. patent application Ser. No. 09/564,069 filed May 3, 2000 to Richards, the subject matter of which is incorporated herein by reference.
2. Related Art
In U.S. Pat. No. 5,680,180 to Huang, a color wheel for a spatial light modulator projection system is disclosed having one green, one red and one blue portion on the wheel. If the color is out of balance, the length of one of the color segments, or the wavelength range of the color segment, can be altered to improve color balance.
In U.S. Pat. No. 5,448,314 to Heimbuch et al., color wheels are disclosed that reduce perceived color separation. One disclosed color wheel has two segments each of red, green and blue, whereas another disclosed wheel has one red, one blue and two green segments.
In U.S. Pat. No. 6,147,720 to Guerinot et al. discloses a projection system with two light sources and a single color wheel. The color wheel can be red, green, blue, cyan, magenta and yellow, or the wheel could be blue cyan and green, or green, cyan, green and blue, depending upon the type of light source and whether the light is reflected or transmitted.
In U.S. Pat. No. 5,650,832 to Poradish et al., discloses a color wheel movable in and out of the path of the light beam, in order to increase brightness of the projected image with a trade-off in color saturation. Also disclosed is a wheel with six segments, three being located radially outward from the other three and having different color saturation values from the inner three segments.
In U.S. Pat. No. 5,233,385 to Sampsell, a color wheel is disclosed that has four segmentsxe2x80x94green, blue, red and white (clear), with the white segment allowing for adding a base level of brightness, which is not controlled. In U.S. Pat. No. 6,054,832 to Kunzman et al, one or two white segments can be used selectively depending upon the frame brightness.
U.S. Pat. No. 5,868,482 to Edlinger et al. discloses structure and features of a prior art color wheel and projection system, the subject matter of which is incorporated by reference.
The present invention is directed to unique light filtering systems. In addition, the present invention is directed to a projection system using more than one sequence of light filters passing through a light beam. Also disclosed is a projection system that allows for changing the brightness or color saturation of the projected image by changing the phase between one sequence of light filters and another.
More particularly a projection system is provided that has a light source for providing a light beam; a spatial light modulator for transmitting or reflecting the light beam to a viewer or target; and two or more color filters provided within the path of the light beam so as to filter the light two or more times before reaching the viewer or target. A projection system can have a multiple wavelength light source; a rotatable mechanical color sequencing device; and a spatial light modulator upon which light from the light source impinges before or after passing through the color sequencing device; wherein the color sequencing device is capable of changing the temporal sequence or duration of the colors that are viewed or directed on a target. Also disclosed is an illumination system that includes a light source; two or more time-repeating filters disposed within a light path of light from the light source; a spatial light modulator disposed in the light path; and projection optics for projecting light filtered by the two or more time-repeating filters and modulated by the spatial light modulator.
Methods are also disclosed for directing light of multiple wavelengths from a light source; dividing over time the light from the light source into time segments, the time segments including a plurality of different color segments and a plurality of brightness enhancing segments, the time segments being time sequentially projected onto a spatial light modulator; projecting an image from the spatial light modulator on a target; and changing the time allotted to the brightness enhancing time segments that are projected onto the spatial light modulator so as to increase the brightness of the image projected onto the target. A method is also disclosed for changing the brightness and/or color saturation of a projection system, comprising providing a projection system having a light source, a spatial light modulator, sequentially moving light filters provided two or more times within a light beam from the light source so as to alter light due to the sequentially moving filters into a series of filtered light time segments over time for each sequence of movable light filters, and projection optics, the light source disposed for providing light incident on the spatial light modulator, and the projection optics disposed for receiving light from the spatial light modulator; directing light from the light source through the projection optics via the spatial light modulator; and changing the brightness and color saturation by changing the movement of at least one sequence of moving light filters relative to at least one other sequence of moving light filters.
In another embodiment, a method is disclosed for changing the brightness and/or color saturation of a projection system, comprising providing a projection system having a light source, a color sequencing device, a spatial light modulator, and projection optics, the light source disposed for providing white light, and the projection optics disposed for receiving light from the spatial light modulator; directing light from the light source through the projection optics via the spatial light modulator and one or more color sequencing devices; wherein the light from the light source is white light and the one or more color sequencing devices causes the white light to be divided into different colors and white light, with the different colors and white light being provided sequentially over time; mechanically altering the position or phase of the one or more color sequencing devices so as to gradually increase or decrease the amount of time during which white light is reflected or transmitted from the one or more color sequencing devices to a target.
In yet a further embodiment of the invention a method is disclosed which includes providing a projection system having a light source, a spatial light modulator, and projection optics, the light source disposed for providing white light or light having multiple wavelengths, and the projection optics disposed for receiving light from the spatial light modulator; directing light from the light source through the projection optics via the spatial light modulator; passing the light within the projection system through a first sequence of colors and white light and passing the sequenced light through a second sequence of colors and white light. In a still further embodiment of the invention, a method is disclosed comprising providing a projection system having a light source, a spatial light modulator, and projection optics, the light source disposed for providing white or substantially white light, and the projection optics disposed for receiving light from the spatial light modulator; directing the white light before or after being incident on the spatial light modulator through a color sequencer to result in light of different colors and white light sequenced over time; and increasing color saturation by allotting less time to white light and more time to one or more of the colors.